呼吸力学的知识

机械通气的呼吸力学Respiratorymechanicsofmechanicalventilation张翔宇SICUShanghaiTenthPeople’sHospitalShanghaiTongjiUniversityShanghai,China呼吸机波形与参数♥压力－pressure♣近端压力♣远端压力♣气管内压力♣食管压力，内源性PEEP♥容量－volume，压力-容量环♥流量－flow，流速-容量环♥呼吸做功，等基本图形FlowVolumePressureP-VloopF-Vloop各压力参数♥吸气峰压（PIP）♣PIP=PRAW+Pplateau♥平台压（Pplateau）♣Pplateau=VT/CRS♥呼气末压（EEP）♥气道阻压（PRAW）♣PRAW=RAW×（flowrate）呼吸力学监测♥顺应性（Compliance）♣静态顺应性（Cst）Cst=VT/（Pplateau—PEEP）♣动态顺应性(Cdyn)Cdyn=VT/（PIP—PEEP）♥气道阻力(RAW)♣RAW=PRAW/(flowrate):2~3(cmH2OL/s)♣包括呼吸道与气管导管的阻力AirwayPressure(VCV)AirwayPressure(VCV)压力WhySpontaneousBreathShouldBeNeeded♥Bettercardiacoutput♥Betterventilation/perfusion♥Betterendexpiratorylungvolume(EELV)♥BetterclinicaloutcomeCurrentOpinioninCriticalCare2005,11:63–68ChristianPutensenAugust,2006CurrentOpinioninCriticalCare2002,8:51–57FabryChest1995:107:1387AsynchronyisstillaproblemPatient-ventilatorasynchronyduringassistedmechanicalventilationArnaudW.ThillePabloRodriguezBelenCabelloFrançoisLelloucheLaurentBrochardIntensiveCareMed(2006)32:1515–1522TiinPSVInspirationterminationCriteria(Esens)25%ofpeakflowinmostcases压力上升时间与吸气终止OvershootsupraplateauIntrathoracicpressuresTRACHEALPRESSUREPROX.AIRWAYPRESSUREPLEURALPRESSUREALVEOLARPRESSURERespLab@MGHAsiaVentForum@ShanghaiTCI亚洲通气论坛ApproximatespleuralpressurePolyethylene10cmlongballoon100cmlongtubingPositionedinthelower1/3oftheesophagusFilledwith0.5-1.0ccairProperplacementoftheballoonisimperativeforaccuratemeasurements.Anapproximatelevelofplacementcanbemadebymeasuringthedistancefromthetipofthenosetothebottomoftheearlobeandthenfromtheearlobetothedistaltipofthexiphoidprocess.BaydurMethod,toconfirmballoonplacementCalculationsbasedondifferentialpressuresTrachealPressureMeasurements•Intendedtypicallyforintermittentuse•Moreaccuratelydisplaysactualpressurestransmittedtotheairways•ProvidesabilitytomeasureimposedWorkandResistanceTrachealPressuresMeasurespressureatdistalendofendotrachealtube5FrpolyethylenetubePAW-PTR/Flow(L/s)=ResistanceofETTAdvanceTrachealPressurecatheterto1cmlessthanETplusadaptersWithdraw1-2cmifpatientcontinuestocoughEvaluationofpressure/volumeloopsbasedonintratrachealpressuremeasurementsduringdynamicconditions;S.Karasonetal,ActaAnesthesiolScand2000;44:571-577Evaluationofpressure/volumeloopsbasedonintratrachealpressuremeasurementsduringdynamicconditions;S.Karasonetal,ActaAnesthesiolScand2000;44:571-577•Tidalvolumeremainsconstant•AsI:Eratioischanged,autoPEEPisseenonlywithtrachealpressures•PIPincreasesandCompliancedecreasesTC,气道阻力与流速的关系051015202501020304050607080FlowRateDeltaP7.5mm导管两端压力差TC/ATCATCHaberthurICM1999;25:514Doesthetube-compensationfunctionoftwomodernmechanicalventilatorsprovideeffectiveworkofbreathingrelief?CriticalCareOctober2003Vol7No5Maedaetal.TC100%,ETT6.5mmPcircuitPesoPplural气管压力监测•设计为间断性监测•更准确地显示气管内压力•能够监测做功与阻力Ptr(trachealpressure)作为压力控制呼吸的向导♥在压力控制通气时，由于气管内插管造成的气流阻力升高，导致肺内压力达不到理想水平♥AVEA可以测量气管内压力，并作为一条曲线显示。♥吸气压力可以根据气管内压进行调节♥Paw=28♥Ptr=25Ptr(trachealpressure)作为压力控制呼吸的向导用气管压和食道压计算力学负担为何测量呼吸功?♥WOBpt测定病人实际的呼吸功水平♣正常.3-.6Joules/Liter♣.3病人做功太低，废用性萎缩♣.75病人可能出现疲劳♥长期机械通气病人脱机成功的关键是能否为他们提供一个正常的呼吸功♣MacIntyre;CritCareMed1999;27:1040♣机器支持的力度应根据病人呼吸功来调节♥AVEA可以提供此类数据用气管压和食道压计算力学负担用气管压和食道压计算力学负担用气管压和食道压计算力学负担Real-timeassessmentofWOB.Pt=25%ofworkVent=75%ofworkEffortisamplifiedbyafactorof4withaproportionalityratioof3:1%Supp75%PAV™+SoftwareOptionClinicalDescriptionD.Georgopoulos,IntensiveCareMed.2008Jul8.FlowAirwayPressureAutoPEEP(AirTrapping)StaticPEEPiEnd-ExpiratoryHoldExpHoldExpHoldSetPEEP=0cmH2OStaticPEEPiStaticPEEPiFlowAirwayPressureProblemswithautoPEEPexpiratoryholdmeasurements♥Willnotworkifpatientisbreathingspontaneously♥Willnotworkifpatienthassmallairwayclosure,(flowdependentairways)♥Falsenegatives1.PatienttriggerworkbeforePEEPapplied2.NotePEEPapplication3.PatienttriggerworkafterPEEPapplied监测由于气流受限而引起的内源性PEEP而增加的触发功F-VloopF-Vloopandleaking漏气Leak,漏气SIMV+PSV，通气管路存在漏气AutoPEEPMIP测量---定义MIP(MaximumInspiratoryPressure，最大吸气压)/P100，测量病人在自主呼吸状态下，压力曲线上的负向最大值。MIP测量---意义正常值:成人-70to-100cmH2O儿童-20to-100cmH2O脱机标准-20cmH2O意义:病人的呼吸力量参数.病人吸气肌力量的标志物.作为脱机以及评价神经肌肉疾病进展情况的标准.在脊柱后侧突，老年，COPD以及神经肌肉疾病的病人会其绝对值会降低。P100测量---定义呼吸驱动(P100),探测到病人吸气努力开始计算，第一个100ms内所形成的最大吸气负压。P100测量---正常值及意义正常值:成人-1to-4cmH2O儿童-0.5to-4cmH2O注意:在吸气已经启动，而吸气阀仍处于关闭状态的前100ms所产生的压力。正常情况下，病人感知气路阻塞所需要的时间为300ms，因此，P100是一个很好的测量呼吸中枢驱动力信号的输出指标。在最初的这300ms时间里，肺容量和气体流量没有改变，因此，肺脏力学的异常对本指标的测量没有影响。超过-5cmH2O意味着呼吸驱动过高，可能会增加呼吸功并导致呼吸肌疲劳。Intra-thoracicpressureswhileplayingmusicalinstrumentsTrans-pulmonaryPressures♥Esophagealballoonpressuresreflectpleuralpressures♥Pleuralpressurescanindicateexternalpressuresworkingagainstthelung♥Trans-pulmonarypressurescanhelpusdeterminesafeventilationandeffectivePEEPNumericalAssessments–Paw,Pes,Ptp–Insp&ExpHoldsTrans-pulmonaryInspiratoryPlateau:♣Obtainalveolardistending(Paw)andchestwall(Pes)pressures♣Paw–PesproducestheTra